# Electrical Circuits Homework

#### MrAl

Joined Jun 17, 2014
6,770
Hi,

40y=210 ??

You should double check that.

What kind of circuit analysis techniques were you taught so far?
Can you combine impedances for example?

#### azathioprin

Joined May 5, 2016
2
Sory my fault, 40y = 280

We learned Thevenin, Norton, Node Voltage and Mesh Current analysis methods. We can use Node Voltage method for first question.
Z for R = R ohm
Z for L = jwL ohm Z for 3H inductor, j*314*3=j942
Z for C = -j/wc ohm (there is no capacitor in the question)
We can take the f is 50 hertz on steady state. So, w=2πf = 2*3.14*50 = 314 rad/s

#### WBahn

Joined Mar 31, 2012
24,964
Since you have (supposedly) learned a number of techniques, then apply those techniques to these circuits. Let's focus on just one problem per thread, so let's focus on the first one and ignore the second one (it should go in a separate thread).

You need to show YOUR best attempt to solve the problem using the techniques you know. Show your work.

Unless you are doing transform methods, using impedances will not help you because (at this point) you probably only know how to use impedances for circuits in sinusoidal steady state while the first problem is a transient response question.

The claim that the circuit is in steady state before the switch is closed is a bit misleading because you have an open-circuited current source, but since we are only interested in what happens to the right of the switch after the switch is closed, we can hold our nose and turn a blind eye to this inconvenient fact.

What is the current in the inductors just before the switch is closed?

What is the current in the inductors just after the switch is closed?

What is the current in the inductors a long time after the switch is closed?

What is the general nature of the current in the inductors after the switch is closed (i.e., what kind of equation describes it)?

#### MrAl

Joined Jun 17, 2014
6,770
Sory my fault, 40y = 280

We learned Thevenin, Norton, Node Voltage and Mesh Current analysis methods. We can use Node Voltage method for first question.
Z for R = R ohm
Z for L = jwL ohm Z for 3H inductor, j*314*3=j942
Z for C = -j/wc ohm (there is no capacitor in the question)
We can take the f is 50 hertz on steady state. So, w=2πf = 2*3.14*50 = 314 rad/s
Hi,

Quick question:

So you are saying that the 10 amp current source is an AC source (50Hz) and you need to find the AC steady state response? I ask because that is different than the transient response.

#### WBahn

Joined Mar 31, 2012
24,964
Sory my fault, 40y = 280

We learned Thevenin, Norton, Node Voltage and Mesh Current analysis methods. We can use Node Voltage method for first question.
Z for R = R ohm
Z for L = jwL ohm Z for 3H inductor, j*314*3=j942
Z for C = -j/wc ohm (there is no capacitor in the question)
We can take the f is 50 hertz on steady state. So, w=2πf = 2*3.14*50 = 314 rad/s
This post wasn't up when I was writing my earlier response.

So are you saying that the current source is a sinusoidal source?

If so, then can we assume that you have learned transform methods, particularly Laplace?

#### shteii01

Joined Feb 19, 2010
4,647
We can take the f is 50 hertz on steady state. So, w=2πf = 2*3.14*50 = 314 rad/s
I doubt it.